With the construction of the 3rd generation mobile communication (3G) network of China is developed progressively, three major mobile communication operators step into the 3G era formally. However, since in the initial stage of the construction of the current 3G network and the following development period, for the coverage level of the 3G network, compared with the 2G network which has already been optimized and improved constantly in more than ten years, there is greater difference in no matter the coverage breadth (the 2G network nearly covers all natural villages of our country) or the coverage depth (such as, indoor, basement and subway and so on), major operators simultaneously regards the long-term dual network co-existence of 2G and 3G as their own operation target and strategy. China Mobile has especially proposed the Three No principle “No card changing, No number changing, No need to register” and all kinds of the Time Division-Synchronous Code Division Multiple Access (TD-SCDMA)/Global system for Mobile Communications (GSM) dual mode and single standby customized cell phone terminal to popularize and run its own TD-SCDMA 3G network.
But the strategy of “co-existence of the 2G and 3G network” and “TD-SCDMA/GSM dual mode and single standby customized terminal” meets the difficulties in the real operation. On one hand, since the existing “2G and 3G dual mode handoff” strategy causes unusual failures, such as the frequent reselection of the cell phone terminal, the serious power consumption, the dropped call, the network being cutoff, even network disconnecting and so on, to take place occasionally and the user experience is worse; on the other hand, since the coverage quality of the existing 3G network is still not so good as the GSM network, which causes that the confidence of the user in the TD-SCDMA network is insufficient. The problem of the network has caused the predicament of the terminal, and conversely, the predicament of the terminal has enlarged the problem of the network.